Direct high temperature sludge energy recuperator transformer module

ABSTRACT

Systems and processes for processing sludge and other natural waste are provided. In one example, the sludge or natural waste may be dried into a powder using high-temperature gas to absorb moisture from the sludge, causing the high-temperature gas to become an at least partially saturated gas. The at least partially saturated gas may pass through a scrubber before being heated in an air-heater and used in the moisture absorption process. The heat for the air-heater may be provided by a burner operable to burn the dried powder obtained from the sludge. The heated gas may be used to pre-heat the saturated gas and may be used to dry additional sludge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to Australian Patentapplication number 2010905078, filed Nov. 16, 2010, entitled “DirectHigh Temperature SERT Module (Sewage Energy Recuperator Transformer),”which is incorporated by reference herein in its entirety.

BACKGROUND

1. Field

This application relates generally to the treatment of semi-solid wastematerials containing organic solids and, more specifically, toprocessing municipal sewage sludge, agricultural waste, and othernatural waste materials containing organic material (hereinafterreferred to as “sludge”) for use as a source of energy.

2. Related Art

Many systems and processes have been developed to treat and dispose ofsludge. For example, many systems and processes include removingmoisture from the sludge and removing or stabilizing contaminants thatmay be harmful to the environment or that may pose substantial healthrisks if not dealt with properly when released into the environment. Themoisture removed from the sludge is referred to herein as “waste water.”Many of these treatment systems and processes for removing moisture andcontaminants from the sludge produce harmful byproducts of their ownthat require special handling for disposal.

The residual semi-solid material that results from waste and wastewatertreatments, animal waste, and the like, is often referred to as“sludge.” In this application, the term “sludge” is also used to referto agricultural food stock waste. Sludge, regardless of its origin, maybe categorized based on the amount of treatment that it has undergone.For example, sludge that has not yet been decomposed by anaerobicbacteria is often referred to as “undigested sludge,” while sludge thathas been decomposed by anaerobic bacteria is often referred to as“digested sludge.” Typically, undigested sludge and raw/fresh animal orfood stock waste have higher calorific values, while digested sludge andaged animal or food stock waste typically has a lower calorific value incomparison.

More specifically, there are two main types of waste treatmentmethods—anaerobic and aerobic. In anaerobic systems, microbes, in theabsence of oxygen, are used to break down the raw waste or undigestedsludge to form methane gas and other byproducts that may be used andmust be properly disposed of. A typical length of time required toprocess waste using an anaerobic treatment system may be about twelve totwenty days.

A treatment plant utilizing an aerobic treatment process, however, maybe able to treat raw, highly contaminated waste or undigested sludge ina single day. Typically, these systems utilize pre-treatment byanaerobic digestion, which may be carried out in an enclosedlow-pressure vessel to break down the waste to allow methane gas to beextracted and prospectively used.

Sludge of all types, for example, undigested sludge, digested sludge,activated sludge, raw or fresh waste, aged waste, and the like (all ofwhich are hereinafter referred to as “sludge”) includes more than 90%waste/moisture and will typically undergo a dewatering process in whicha portion of the moisture may be removed and the liquid directed (i)back to and commingled with wastewater for treatment prior to disposalor discharge, or (ii) to holding lagoons where it will evaporate ormigrate into the groundwater table. The dewatered sludge may be moreefficiently processed since all types of sludge require processingbefore disposal.

Thus, systems and processes for the treating and disposing of sludge aredesired.

SUMMARY

In one exemplary embodiment, a system for processing dewatered sludge isprovided. In some examples, the system may include either a mill orgrinder operable to receive high-temperature gas, receive sludge, andreduce the moisture content of the sludge to break the sludge into adried powder in the presence of the high-temperature gas, wherein thehigh-temperature gas absorbs at least a portion of the moisture contentof the sludge to become at least partially saturated gas. The system mayfurther include a first separator operable to separate the dried powderfrom the at least partially saturated gas and a condenser operable toreduce a moisture content of the at least partially saturated gas byreducing the temperature below the vaporization point of the at leastpartially saturated gas. The system may further include a heateroperable to heat the reduced-temperature gas to generate heated gas, asecond separator operable to separate at least a portion of ash from theheated gas, wherein the second separator is further operable to direct afirst portion of the heated gas to the mill or grinder to be used in themill or grinder as the high-temperature gas to dry the sludge as it ismilled or grinded, and an output system operable to discharge the ashand, in one example, to discharge a second portion of the heated gasfrom the system or, in another example, to recover heat from this heatedgas by using the recovered heat to pre-heat the ambient air that is usedin the burner and/or pre-heat the sludge prior to it entering thegrinder or mill.

In some examples, the sludge may include digested sludge, undigestedsludge, fresh animal waste, aged animal waste, or agricultural foodwaste. In some examples, the concentration of inert gas in thehigh-temperature gas may be sufficient to reduce the chance ofcombustion or explosion. In yet other examples, the high-temperature gasmay have a temperature sufficient to deodorize and sterilize the processgas.

In some examples, the heater may include an air-heater jacket operableto receive the reduced-temperature gas from the first condenser, whereinthe air-heater jacket is further operable to cause thereduced-temperature gas to travel over at least a portion of a surfaceof the heater. In other examples, the air-heater jacket may be replacedwith a separate pre-heater.

In some examples, the heater may include a burner operable to burn amixture of ambient air and at least a portion of the dried powder asfuel. The burner may be further operable to burn an oil or gas,separately or in combination with the dried powder fuel. The system mayfurther include a mixing valve operable to combine the mixture ofambient air and one or more of the above described fuels with a portionof the heated gas not directed to the grinder or mill by the tappingduct. The weight of the ambient air may be equal to a weight of thesecond portion of the heated gas that is discharged by the outputsystem.

In some examples, the first condenser may be operable to receive waterat a first temperature, the water to be used to reduce the temperatureof the at least partially saturated gas, wherein the first condenser maybe further operable to output the water at a second temperature that ishigher than the first temperature.

In some examples, the output system includes a water-mist-cooling systemoperable to reduce a temperature of the second portion of the heated gasto form cooled gas. The output system may further include a thirdseparator operable to separate at least a portion of ash contained inthe cooled gas from the cooled gas, wherein the third separator isfurther operable to discharge the ash separated from the cooled gas fromthe system. The output system may further include a second condenseroperable to reduce a moisture content of the cooled gas by reducing atemperature of the cooled gas to form a reduced moisture gas and a fanoperable to discharge the reduced moisture gas from the system. In someexamples, warmed water from the second condenser may be used to pre-heatthe sludge before entering the grinder or mill.

In another exemplary embodiment, another system for processing dewateredsludge is provided. In some examples, the system may include a mill orgrinder operable to receive high-temperature gas, receive sludge, andreduce a moisture content of the sludge by breaking the sludge into adried powder in the presence of the high-temperature gas, wherein thehigh-temperature gas absorbs at least a portion of the moisture contentof the sludge to form at least partially saturated gas. The system mayfurther include a first separator operable to separate the dried powderfrom the at least partially saturated gas and a condenser operable toreduce a moisture content of the at least partially saturated gas byreducing a temperature of the at least partially saturated gas to form areduced-temperature gas. The system may further include a pre-heateroperable to pre-heat the reduced-temperature gas to form pre-heated gas,a heater operable to heat the pre-heated gas to further heat the heatedgas, and a second separator operable to separate at least a portion ofash from the heated gas. The system may further include a first tappingduct operable to recirculate at least a portion of the heated gas bydirecting the at least a portion of the heated gas to the mill orgrinder, wherein the at least a portion of the heated gas is to be usedin the mill or grinder as the high-temperature gas.

In some examples, the first tapping duct may be operable to recirculatea majority of the heated gas received at the tapping duct. In otherexamples, the high-temperature gas may have a temperature sufficient todeodorize and sterilize the process gas.

In some examples, the pre-heater may be operable to pre-heat thereduced-temperature gas using at least a portion of the heated gas thatis not directed to the mill or grinder by the tapping duct. In otherexamples, the portion of the heated gas that is not directed to the millor grinder may be either utilized to pre-heat the sludge before it ismilled/grinded or removed from the system.

In some examples, the heater may include a burner operable to combust amixture of ambient air and at least a portion of the dried powder, oil,or gas. In other examples, the heater may include an air-heater jacketoperable to receive the pre-heated gas from the pre-heater, wherein theair-heater jacket is further operable to cause the pre-heated gas totravel over at least a portion of a surface of the heater.

In some examples, the system may further include a mixing valve operableto combine the mixture of ambient air and the at least a portion of thedried powder or other fuel with a portion of the heated gas not directedto the mill or grinder by the first tapping duct. In other examples, thesystem may further include a second tapping duct operable to direct, tothe mixing valve, the portion of the heated gas not directed to the millor grinder.

In other exemplary embodiments, processes and computer-readable storagemediums are provided for processing sludge using the systems describedabove.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a block diagram of an exemplary system for treatingsludge.

FIG. 2 illustrates a block diagram of another exemplary system fortreating sludge.

FIG. 3 illustrates a block diagram of another exemplary system fortreating sludge.

FIG. 4 illustrates a block diagram of another exemplary system fortreating sludge.

FIG. 5 illustrates a block diagram of another exemplary system fortreating sludge.

FIG. 6 illustrates a block diagram of another exemplary system fortreating sludge.

FIG. 7 illustrates a block diagram of another exemplary system fortreating sludge.

FIG. 8 illustrates an exemplary dual fuel burner and air heater.

FIG. 9 illustrates an exemplary process for treating sludge.

FIG. 10 illustrates an exemplary computing system that may be used tocontrol a sludge treatment system.

DETAILED DESCRIPTION

The following description is presented to enable a person of ordinaryskill in the art to make and use the various embodiments. Descriptionsof specific devices, techniques, and applications are provided only asexamples. Various modifications to the examples described herein will bereadily apparent to those of ordinary skill in the art, and the generalprinciples defined herein may be applied to other examples andapplications without departing from the spirit and scope of the variousembodiments. Thus, the various embodiments are not intended to belimited to the examples described herein and shown, but are to beaccorded the scope consistent with the claims.

FIG. 1 illustrates a block diagram of an exemplary treatment system 100.As an overview, treatment system 100 may be used to treat sludge byconverting waste/sludge into a powder having a high calorific value thatis suitable for combustion in suspension or that may be used as afertilizer. The treatment system 100 may be capable of processingvarious types of sludge, for example, digested sludge, undigestedsludge, raw waste, fresh waste, aged waste, or combinations thereof.Treatment system 100 may also be used to treat agricultural food wastes,which are herein included in the term “sludge.”

Treatment system 100 may include a storage unit 1 for holding sludge. Insome examples, storage unit 1 may be used to store sludge that has beendewatered to have an approximate 15% to 25% solids content. However, itshould be appreciated that sludge having other content ratios may beused. Storage unit 1 may include any type of standard storage systemsuitable for storing sludge. The volume of storage unit 1 may depend onthe location of treatment system 100 and “feed stock.” For instance, iftreatment system 100 is situated at a municipal wastewater treatmentplant or large-scale agricultural operation with an adequate continuoussupply of sludge and onsite dewatering, storage unit 1 may be used onlyas a surge bin having a two to three hour sludge capacity since thetreatment system 100 may be fed by the plant's sludge dewateringequipment. If, however, the treatment system 100 is at a treatment plantwhere the supply of sludge is not adequate for efficient operation ofthe system on a continuous basis, such as at a hog farm, cattle ranch,farm, or dairy with sludge being trucked in from other sites, thestorage unit 1 may have a volume allowing storage of a 24-hour or morerunning capacity of wet sludge (e.g., between about 15%-25% solids).However, it should be appreciated that, irrespective of the examplescited, a storage unit 1 having any desired capacity may be used.

Treatment system 100 may further include a grinder or mill 2 in whichthe moisture may be removed from the sludge that has been dewatered(either at the treatment site or offsite). The grinder or mill 2 mayalso be used to process the sludge to a uniform, or at leastsubstantially uniform, size. In some examples, the feed stock of sludgemay be pre-heated with process water of any temperature via a heatexchanger (similar to sludge pre-heater 61 shown in FIG. 2). In someexamples, treatment system 100 may receive high-temperature gas andsludge from storage unit 1. Prior to entering grinder or mill 2, thehigh-temperature gas and either the sludge or pre-heated sludge may becombined at mixing duct 3. Mixing duct 3 may be the point at which wetsludge or wet pre-heated sludge is introduced to the system and mixedwith hot drying gas. Here, evaporative cooling may take place as thesetwo products are exposed to one another. Mixing duct 3 may be made of amaterial capable of withstanding both the high-temperature of the gasand the potentially corrosive nature of either the wet sludge or dryinggas. For example, mixing duct 3 may be made of stainless steel or otherappropriate material.

In some examples, the sludge may be transferred from storage unit 1using an auger actuated moving floor system or an alternate means thatis capable of delivering an accurate, modulated supply of sludge to thegrinder or mill 2. For example, the auger may be capable of deliveringpreviously dewatered, but otherwise wet, sludge. The main feed auger mayhave a length sufficient to feed sludge from a storage unit 1, which maybe located separate from, but adjacent to, the grinder or mill 2. Asmentioned above, in some examples the sludge may be pre-heated byprocess water using a water-to-sludge heat exchanger (not shown) beforeentering grinder or mill 2.

After being combined at mixing duct 3, the combined high-temperature andreduced moisture gas and sludge (pre-heated sludge or non-pre-heatedsludge) may be transferred to grinder or mill 2. The grinder or mill 2may include a simplex or duplex design and may be configured topulverize the sludge into a fine powder with a moisture content of lessthan about 10%. In some examples, grinder or mill 2 may be operable toprocess on the order of 60 tons of wet sludge (15%-25% solids) over a24-hour period by flash drying and milling or grinding the sludge to afine powder with a moisture content of less than 10%, for example,3%-5%. However, the treatment system may be of any capacity (size) andmay reduce the moisture of the sludge to any amount.

In some examples, the grinder or mill 2 may receive high-temperature gashaving a temperature sufficient to deodorize and sterilize the processgas. It should be appreciated that this temperature may vary dependingon the specific application. The use of high-temperature gas in grinderor mill 2 enables increased moisture pickup per unit weight of dry gas.As a result, the throughput of grinder or mill 2 may be increased inspite of reduced heat input to the grinder or mill 2. Due to theevaporative cooling that occurs within the grinder or mill 2, thetemperature of the gas stream may be reduced before exiting the grinderor mill 2. Since the gas may be recirculated exhaust from the dual fuelburner 13, it may be low in oxygen and high in inert gasses (nitrogenand carbon dioxide), thereby reducing the chances of unwanted combustionduring drying.

In some examples where grinder or mill 2 includes a duplex mill design,grinder or mill 2 may include an initial stage having one or moremacerators for breaking up the sludge in the presence of thehigh-temperature and low-moisture gas to cause the high-temperature gasto draw moisture from the sludge by evaporative cooling. The duplexgrinder or mill 2 may further include an attrition stage having multiplestages of rotating blades arranged such that each side of the duplexgrinder or mill 2 may contain blades that revolve in opposite directions(i.e., turning into each other) to form an intensive field of particlestraveling at velocities high enough to keep the milled sludge insuspension. In some examples, the arrangement of circulating blades mayinclude a boss carrying these blades such that each stage will have asplit phase to ensure that the gas flow carrying the particlesintercepts each blade to achieve higher velocity of the particleswithout shock. Shock may be prevented or reduced by ensuring that theblade rotation is brought together at the same or similar velocity. Insome examples, each casing of the duplex design may be fitted withgrinding bars arranged to have a slight lead in the production of gasflow from the inlet to the outlet of the grinder or mill 2 to obviateblockage and particles being built up and lodged between the grindingbars.

Treatment system 100 may further include gas-solids separator 4 forseparating particulate from the conveying gas received from grinder ormill 2. In some examples, gas-solids separator 4 may be configured toreceive the dried powder formed from the sludge and the gas streamcarrying the sludge moisture from grinder or mill 2. Gas-solidsseparator 4 may be configured to separate the dried powder from the atleast partially saturated gas flow and deposit the separated powder in adry fuel bin 5. In some examples, gas-solids separator 4 may be madefrom a material capable of withstanding high gas temperatures andcorrosive materials, such as stainless steel or other appropriatematerials, and may be operable to remove at least 90% of the solids fromthe gas stream. Solids may be dropped via a rotary valve into the dryfuel bin 5 or by any other means.

In some examples, gas-solids separator 4 may be a cellular-typeseparator. In these examples, the inlet to each individual cell may befitted with a multiple blade spinner arranged to spin the gases andconvey the particles to the outlet of the cell. The particles may, forexample, be deposited into dry fuel bin 5 while the clean conveying gasmay pass to a condensing-type scrubber 7. For instance, while anypercentage of gas and moisture may be utilized, in some examples, about75% of the gas and moisture received from grinder or mill 2 may passdirectly over to condensing-type scrubber 7, while the remainingpercentage of the gas and moisture may be vented off a secondary side ofgas-solids separator 4 to high-efficiency cyclones 6. In other examples,the remaining percentage of the gas and moisture may instead be used topre-heat the ambient air supply entering the dual fuel burner 13 via anair-to-air heat exchanger (not shown).

In some examples, cyclones 6 may include a Stairmand-typehigh-efficiency cyclone to clean the vented gas at the secondary side ofgas-solids separator 4. Specifically, two cyclones, each made fromtemperature and corrosion-resistant materials (e.g., stainless steel),may be used to separate the particles from the conveying gas of thevented gas stream and may discharge the solids to dry fuel bin 5. Thecleaned gas may then rejoin the main gas stream entering condensing-typescrubber 7. While the above examples were described using Stairmand-typecyclones, other similar cyclone separators or other gas solidsseparators capable of functioning effectively and safely in theoperating temperatures may be used to clean the gas vented from thegas-solids separator 4.

As mentioned above, once separated from the gas stream, the driedpowder, which is now a biofuel, may be stored in dry fuel bin 5. In someexamples, dry fuel bin 5 may be isolated from the separators by, forexample, rotary valves. Additionally, as described in greater detailbelow, in some examples, dry fuel bin 5 may include an auger that metersthe dried powder through a venturi (e.g., fuel venturi 15) to the dualfuel burner 13 at a rate sufficient to provide enough heat for airheater 12. It should be appreciated that any rate may be used dependingon the fuel mixture and other objectives of the system. Dry fuel bin 5may also include an output auger for removing excess dried powder fromtreatment system 100 at system exit 33 for use in other systems orprocesses, for example, as a fuel. In some examples, dry fuel bin 5 mayalso include a safety system to prevent dust explosions. The safetysystem may reduce the possibility of dust explosions by, for example,injecting an inert gas, such as nitrogen or carbon dioxide, into dryfuel bin 5. Dry fuel bin 5 may be made of a material capable ofwithstanding high temperatures, such as stainless steel or otherappropriate materials.

As mentioned above, treatment system 100 may further include acondensing-type scrubber 7 for removing moisture and leftoverparticulate from the at least partially saturated gas produced bygas-solids separator 4 and cyclones 6. The shell of condensing-typescrubber 7 may be made from a high-temperature and corrosion-tolerantmaterial, such as stainless steel or other appropriate materials.Condensing-type scrubber 7 may receive the at least partially saturatedgas leaving gas-solids separator 4 and cyclones 6, as well as water froman ambient water source 8. The moisture in the at least partiallysaturated gas may be removed by lowering the temperature of this gas tobelow its vaporization point by the lower-temperature ambient water,causing it to condense out of the gas stream. As the moisture condensesinto water, it may collect carry-over particulate remaining in the gasstream and carry the particulate out of the system through system exit10. Additionally, after the ambient water from ambient water source 8 isused to cool the gas stream, the warmed ambient water may exit thesystem through system exit 9. In other examples, as shown in FIG. 2,instead of exiting the system through system exit 9, the warmed ambientwater may be used to pre-heat the sludge/feed stock before it entersgrinder or mill 2.

In some examples, the at least partially saturated gas received fromgas-solids separator 4 and cyclones 6 may be passed over a series oftubes that are cooled by the flow of water from ambient water source 8,causing the gas temperature to drop. As the cooled temperature is lowerthan the dew point of the moisture, the moisture will condense out ofthis gas. In some examples, condensing-type scrubber 7 may includemultiple layers of ripple-fin tube coils. These tubes may be cooled bywater fed from an ambient water source 8 at a rate controlled to reducethe temperature of the incoming gas to a tepid temperature.

Treatment system 100 may further include system circulation fan 11 fordrawing the cooled gas or air from condensing-type scrubber 7 andcirculating it through the jacket 50 of air heater 12. In some examples,circulating fan 11 may be made from temperature and corrosion-tolerantmaterials, such as stainless steel or other appropriate materials, andmay circulate 100% of the weight of gas that passes through treatmentsystem 100. In some examples, the gas may be drawn from condensing-typescrubber 7 by system circulating fan 11 and may then be passed to thejacket 50 of air heater 12. The use of a single fan for therecirculation of gas in treatment system 100 provides ease of control,although the system may utilize more than one fan or no fans at all.System circulation fan 11 may include a speed control that may beadjusted based on the fuel used.

In some examples, the gas circulated by system circulation fan 11 may bepassed to the air-heater 12 where it may be heated to a temperature andfor a duration sufficient to deodorize and sterilize the process gas bydual fuel burner 13. In other examples, the gas may not be deodorized orsterilized. Air-heater 12 may include two shells that form a jacket 50.The jacket 50 may allow less insulation to be used on the outer surfaceof air-heater 12, and also pre-heats incoming gas before entering theinner shell of air-heater 12. Alternatively, an air-heater design(described in greater detail below) including ceramic or otherrefractory tiles may be used for the air-heating portions of theprocess.

Gas from system circulation fan 11 may enter the jacket 50 of air-heater12 at the end opposite the dual fuel burner 13. The gas may then passthrough the jacket 50 wherein the gas may twist as it passes over thesurface of the inner shell of air-heater 12 towards the dual fuel burner13 end of the jacket 50. This may cool the inner shell of air-heater 12while heating the circulating gas prior to entering the inner shell ofair-heater 12. The resultant lower-temperature of the inner shell ofair-heater 12 may not result in “clinker” formation. In some examples,the gas passing through the jacket 50 may be heated to a temperature ofabout 300° C. prior to entering air-heater 12. The gas may then passinto the inner shell of air-heater 12 where it may be heated by the dualfuel burner 13 to a temperature sufficient for the length of the heatingchamber so that the gas may be adequately heated for the specifictreatment application.

Air-heater 12 may be made from temperature and corrosion-tolerantmaterials, such as high-temperature stainless steel, ceramic lining, orother appropriate materials, and may operate at a through air velocityequal to several times the floating velocity of the ash particles toprevent particulate deposit in the heater (i.e., “clinker”). Using ahigh-temperature stainless steel, ceramic lining, or other similarmaterial may allow a smooth internal shell to be presented to the gasesand may limit the reduction in velocity over the shell that may occurwhen more conventional insulation is employed. Additionally, thediameter and length of the air-heater 12 can be designed to keep the gasvelocity greater than the floating velocity of the ash particles whilenot adversely affecting the flame velocity to overheat theflame-producing clinker from the ash.

As mentioned above, dual fuel burner 13 may be used to heat the gas inair-heater 12. The dual fuel burner 13 may utilize any or a combinationof multiple fuels. The primary source may be the dried powder biofuelsupplied from the dry fuel storage unit 5. The secondary source may be asupplementary fuel source 18, such as gas or oil. The amount of fuelsupplied to dual fuel burner 13 may be controlled to maintain a desiredoutlet temperature for grinder or mill 2. Additionally, the dual fuelburner 13 may be able to supply 100% of the heat required on eitherbiofuel or supplementary fuel alone. In some examples, dual fuel burner13 may include a separate light-up burner, which may be fired by eitheroil or gas for light-up purposes. In some examples, the separatelight-up burner may be used to maintain the system temperature in astand-by mode during times when sludge is not available for the process.

The dual fuel burner 13 may be supplied with biofuel and air from acombustion supply fan 14. In some examples, combustion supply fan 14draws ambient air from the atmosphere through a primary air supply inlet16 and fuel venturi 15. In some examples, this ambient air for dual fuelburner 13 may be pre-heated by exhaust air from the gas-solids separator4 via an air-to-air heat exchanger (not shown). The fuel venturi 15 mayinclude a venturi valve arranged to mix the ambient air from primary airsupply inlet 16 with dried power from dry fuel bin 5 or supplementalfuel from supplementary fuel source 18. Primary air supply inlet 16 mayinclude an air-to-air heat exchanger system (not shown), as well as afilter and grill fitted with an integral adjustable baffle to controldownstream pressure. Combustion supply fan 14 may include a dusthandling fan and may supply the dual fuel burner 13 with the mix ofambient air and the dried powder metered from the dry fuel storage unit5. In some examples, combustion supply fan 14 may include a variablespeed drive to control the airflow to dual fuel burner 13.

In some examples, the weight of ambient air that enters dual fuel burner13 through primary air supply inlet 16 may be equal to approximately10%-40% of that entering dual fuel burner 13. In these examples, theremaining air entering dual fuel burner 13 may enter through secondaryair supply inlet 17. Primary and secondary air supply inlets 16 and 17may each include a filter and grill fitted with an integral adjustablebaffle to control the amount of air entering treatment system 100 andthe downstream pressure.

Since the output of dual fuel burner 13 is mixed with the gascirculating through treatment system 100, the concentration of inert gas(e.g., CO₂ and nitrogen) may increase, advantageously maintaining thetemperature of air-heater 12 to below the softening point of the ashcontent of the sludge.

Treatment system 100 may further include a grit arrestor 19 forreceiving the heated gas from air-heater 12 and for removing ash fromthe gas stream. In some examples, gases leaving air-heater 12 maycontain a high percentage of grit because the dried powder may have theinorganic material content of its feed stock. In some examples, gritarrestor 19 may be similar in design to gas-solids separator 4, exceptthat it may include an increased number of cells and may be manufacturedfrom materials that are both corrosion and temperature-tolerant.

In some examples, a significant percentage of the gas entering gritarrestor 19 may be cleaned and directed to mixing duct 3 and grinder ormill 2. Ash and the remaining gas may be vented off the secondary sideof grit arrestor 19 to be used to pre-heat the ambient air going to thedual fuel burner 13 (as described below with respect to FIG. 2) or maybe vented off the secondary side of grit arrestor 19 to an output systemto be surplussed from the treatment system 100. Specifically, the ashand the gas entering grit arrestor 19 may be directed to an outputsystem having a water-mist-cooling system 20, ash cyclones 22, terminalcondensing scrubber 24, terminal fan 28, and final discharge stack 29.In other examples, a portion of the cleaned gas output by grit arrestor19 may be directed to a hot wind box by a gas diverter valve (similar tohot wind box 63 and gas diverter valve 65 shown in FIG. 2) to pre-heatthe ambient air from secondary air supply inlet 16.

Water-mist-cooling system 20 may include nozzles, pumps, and monitoringequipment for generating a water spray to reduce the temperature of thereceived gas to a temperature sufficient to re-vaporize the moisture inthe partially saturated gas drawn out of the feed stock. The water spraymay be generated using water from a filtered ambient water supply 21.

The cooled gas from water-mist-cooling system 20 may be directed to ashcyclones 22. Ash cyclones 22 may be similar or identical to cyclones 6,and may be used to remove ash from treatment system 100 via ashreticulation 23. Ash reticulation 23 may include an augur to remove ashfrom the system to dry fuel bin 5.

The gas exiting ash cyclones 22 can be directed to terminal condensingscrubber 24. Terminal condensing scrubber 24 may be similar or identicalto condensing-type scrubber 7 and may be used to condense moisture outof the gas received from ash cyclones 22. For instance, terminalcondensing scrubber 24 may direct the gas received from ash cyclones 22over a series of tubes that are cooled by the flow of water from ambientwater source 25, causing the gas temperature to drop below itsvaporization point. As the moisture condenses into water, it may collectcarry-over particulate remaining in the gas stream and carry theparticulate out of the system through system exit 27. Additionally, insome examples, the warmed ambient water from ambient water source 25 mayexit the system through system exit 26. In other examples, as shown inFIG. 2, the warmed ambient water from terminal condensing scrubber 24may be used to pre-heat the sludge/feed stock before it enters grinderor mill 2.

Treatment system 100 may further include a terminal fan 28 for drawingthe surplussed gas through the ash cyclones 22 and terminal condensingscrubber 24. The output of terminal fan 28 may be discharged from thesystem through final discharge stack 29.

In some examples, the weight of gas that enters treatment system 100from the atmosphere through primary and secondary air supply inlets 16and 17 may be equal to the weight of gas that is removed from the systemat final discharge stack 29. As a result, a constant weight of gascirculating through the system may be maintained.

FIG. 2 illustrates a block diagram of another exemplary treatment system200. Treatment system 200 may be similar to treatment system 100, withthe differences discussed in greater detail below. Reference numbers forcomponents of treatment system 200 that are the same as those used forcomponents in treatment system 100 indicate that a similar component maybe used in treatment system 200.

Specifically, system 200 may include gas diverter valve 65 for divertinga portion (e.g., 25%) of the gas cleaned by grit arrestor 19 to hot windbox 63 to be used to pre-heat the ambient air from secondary air supplyinlet 16 before it enters dual fuel burner 13. The remaining portion ofthe gas cleaned by grit arrestor 19 may be directed to mixing duct 3 andgrinder or mill 2. Additionally, as mentioned above, the warmed ambientwater from condensing-type scrubber 7 and terminal condensing scrubber24 may instead be directed to sludge pre-heater 61 to be used topre-heat the sludge/feed stock before it enters grinder or mill 2.

FIG. 3 illustrates a block diagram of another exemplary treatment system300. Treatment system 300 may be similar to treatment system 100, withthe differences discussed in greater detail below. Reference numbers forcomponents of treatment system 300 that are the same as those used forcomponents in treatment system 100 indicate that a similar component maybe used in treatment system 300.

Unlike treatment system 100, treatment system 300 may not includecyclones 6, and may instead direct the output of gas-solids separator 4to condensing-type scrubber 7. Additionally, unlike treatment system100, treatment system 300 may include pre-heater 40. In some examples,the gas may be drawn from condensing-type scrubber 7 by systemcirculation fan 11 and may then be passed to pre-heater 40.

Pre-heater 40 may heat the gas stream from condensing-type scrubber 7through the use of a special duct arranged to pre-heat moisture-freegases. Pre-heater 40 may be made from temperature and corrosion-tolerantmaterials, such as stainless steel or other appropriate materials. Thepre-heated gas may then pass to the air-heater 12 where it may be heatedby dual fuel burner 13. Unlike the air-heater 12 used in treatmentsystem 100, the air-heater 12 used in treatment system 300 may notinclude an air-heater jacket 50. Thus, in some examples, the pre-heatedair from pre-heater 40 may flow directly into the inner chamber ofair-heater 12. In some examples, the shell of air-heater 12 may beinsulated using white wool fiber or another insulating material.

Unlike treatment system 100, treatment system 300 may not includesecondary air supply inlet 17. Thus, 100% of the air for dual fuelburner 13 enters the burner through combustion fan 14. Additionally,unlike treatment system 100 in which the excess ash and gas may bedirected from grit arrestor 19 to water-mist-cooling system 20, in someexamples, excess ash removed by the grit arrestor 19 of treatment system300 may be removed from the system at system exit 42.

In treatment system 300, the gas exiting grit arrestor 19 may bedirected to tapping duct 43. In some examples, tapping duct 43 may beconfigured to direct a majority (e.g., more than 50% and, in someexamples, between 70%-75%) of the gas that leaves grit arrestor 19 tomixing duct 3 and the input of grinder or mill 2. There, therecirculated gas may provide the heat used to dry the sludge in grinderor mill 2. The remaining gas from grit arrestor 19 may be diverted bytapping duct 43 towards mixing valve 41, where the diverted gas may becombined with filtered air or ambient air from atmosphere 44. In someexamples, mixing valve 41 may include a venturi valve. In some examples,combining the diverted gas stream with the filtered or ambient air fromatmosphere 44 may cause the temperature of the diverted gas stream to belowered. This gas stream may then be drawn around the outside of thepre-heater 40 duct arrangement by terminal fan 28 to pre-heat the gaswithin pre-heater 40. The gas stream drawn around the outside ofpre-heater 40 may have its temperature reduced before being dischargedto the atmosphere via final discharge stack 29. In some examples, thegas stream drawn around the outside of pre-heater 40 may pass through anadditional scrubber to reduce emissions and recover additional energy inthe form of heated water before being discharged to the atmosphere viafinal discharge stack 29. Alternatively, in other examples, the gasstream drawn around the outside of pre-heater 40 may be used to pre-heatthe ambient air entering dual fuel burner 13.

In other examples, a portion of the cleaned gas output of grit arrestor19 may be directed to a hot wind box by a gas diverter valve (similar tohot wind box 63 and gas diverter valve 65 shown in FIG. 2) to pre-heatthe ambient air from secondary air supply inlets 16. The remainingportion of the cleaned gas output of grit arrestor 19 may be directed totapping duct 43.

In other examples, treatment system 300 may include a heat exchanger(similar to sludge pre-heater 61 shown in FIG. 2) to pre-heat thedewatered sludge before entering grinder or mill 2.

In some examples, the weight of gas that enters treatment system 300from primary air supply inlet 16 may be equal to the weight of gas thatis tapped off the system at tapping duct 43 to be cooled and releasedfrom treatment system 300 into the atmosphere via final discharge stack29. As a result, a constant weight of gas may be maintained in treatmentsystem 300.

FIG. 4 illustrates a block diagram of another exemplary treatment system400. Treatment system 400 may be similar to treatment system 300, exceptthat air-heater 12 may include an air-heater jacket 50 similar to thatdescribed above with respect to treatment systems 100 and 200. Thus, insome examples, hot gas from the pre-heater 40 may enter an air-heaterjacket 50 where it may circulate around the outside of air-heater 12before entering the inner chamber of air-heater 12. In some examples,the gas passing through jacket 50 may be heated to an intermediatetemperature after exiting jacket 50 and prior to entering air-heater 12.The gas may then pass into the inner shell of air-heater 12 where it isfurther heated by the dual fuel burner 13. In some examples, the gas maybe heated by dual fuel burner 13 to a temperature and for a durationsufficient to deodorize and sterilize the process gas when deodorizingor sterilizing are desired.

In other examples, a portion of the cleaned gas output of grit arrestor19 may be directed to a hot wind box by a gas diverter valve (similar tohot wind box 63 and gas diverter valve 65 shown in FIG. 2) to pre-heatthe ambient air from secondary air supply inlets 16. The remainingportion of the cleaned gas output of grit arrestor 19 may be directed totapping duct 43.

In other examples, treatment system 400 may include a heat exchanger(similar to sludge pre-heater 61 shown in FIG. 2) to pre-heat thedewatered sludge before entering grinder or mill 2.

FIG. 5 illustrates a block diagram of another exemplary treatment system500. Treatment system 500 may be similar to treatment system 300, exceptthat a tap may be taken off the duct 51 between the mixing valve 41 andpre-heater 40. The gas diverted at duct 51 may be directed to a dualfuel air supply mixing valve 52 where it may be mixed with the ambientair carrying the dried powder from fuel venturi 15. By combining the gasfrom duct 51 with the ambient air carrying the dried powder from fuelventuri 15, the ambient air may be pre-heated prior to entering dualfuel burner 13. This may increase the efficiency of the burner 13 whilereducing the oxygen level of the air to the burner 13 to avoid theproduction of clinker from the fuel's ash.

In other examples, a portion of the cleaned gas output of grit arrestor19 may be directed to a hot wind box by a gas diverter valve (similar tohot wind box 63 and gas diverter valve 65 shown in FIG. 2) to pre-heatthe ambient air from secondary air supply inlets 16. The remainingportion of the cleaned gas output of grit arrestor 19 may be directed totapping duct 43.

In other examples, treatment system 500 may include a heat exchanger(similar to sludge pre-heater 61 shown in FIG. 2) to pre-heat thedewatered sludge before entering grinder or mill 2.

FIG. 6 illustrates a block diagram of another exemplary treatment system600. Treatment system 600 may be similar to treatment system 300, exceptthat air-heater 12 may include an air-heater jacket 50 as shown intreatment systems 100, 200, and 400. Additionally, treatment system 600may include a tap taken off duct 51 as shown in treatment system 500.

In other examples, a portion of the cleaned gas output of grit arrestor19 may be directed to a hot wind box by a gas diverter valve (similar tohot wind box 63 and gas diverter valve 65 shown in FIG. 2) to pre-heatthe ambient air from secondary air supply inlets 16. The remainingportion of the cleaned gas output of grit arrestor 19 may be directed totapping duct 43.

In other examples, treatment system 600 may include a heat exchanger(similar to sludge pre-heater 61 shown in FIG. 2) to pre-heat thedewatered sludge before entering grinder or mill 2.

FIG. 7 illustrates a block diagram of another exemplary treatment system700. Treatment system 700 may be similar to treatment system 100, exceptthat exemplary treatment system 700 may not include cyclones 6 and mayinstead direct the output of gas-solids separator 4 to condensing-typescrubber 7. Additionally, unlike the air-heater 12 used in treatmentsystem 100, the air-heater 12 used in treatment system 700 may notinclude an air-heater jacket 50. Thus, in some examples, the output fromcondensing-type scrubber 7 may flow directly into the inner chamber ofair-heater 12. Treatment system 700 may further include system exit 42for removing excess ash from the system instead of outputting the ash towater-mist-cooling system 20 as is done in system 100. Furthermore, insystem 700, the output of grit arrestor 19 can be directed to tap 70where a portion of the output may be directed to water-mist-coolingsystem 20. The remaining portion of the output is directed to mixingduct 3 and grinder or mill 2. Finally, system 700 may not include ashcyclones 22. Thus, the output of water-mist-cooling system 20 mayinstead be directed to terminal condensing scrubber 24.

In other examples, a portion of the cleaned gas output of grit arrestor19 may be directed to a hot wind box by a gas diverter valve (similar tohot wind box 63 and gas diverter valve 65 shown in FIG. 2) to pre-heatthe ambient air from secondary air supply inlets 16. The remainingportion of the cleaned gas output of grit arrestor 19 may be directed totap 70.

In other examples, treatment system 700 may include a heat exchanger(similar to sludge pre-heater 61 shown in FIG. 2) to pre-heat thedewatered sludge before entering grinder or mill 2.

FIG. 8 illustrates an exemplary dual fuel burner and air heater that maybe used as dual fuel burner 13 and air heater 12 in the examplesprovided above. Ducted gas from system circulation fan 11 may be broughtinto the burner through wye 801. A portion of the ducted air may enterburner 13 and may be controlled by an actuated damper. The remainder ofthe ducted air may be directed down the other branch of wye 801 into acollection box for even distribution around combustion chamber 803. Inthis way, the amount of air and fuel into burner 13 can be controlledmore precisely to complete combustion without having to controlcombustion with additional air.

In some examples, the inside of combustion chamber 803 may be lined withrefractory tiles or another insulating material. Additionally, thecombustion chamber 803 may be centered inside the air heater shell. Airheater 12 may further include a bellows-type expansion joint having rodsexternally preventing the shell from expanding and keeping expansioneven.

FIG. 9 illustrates an exemplary process 900 for treating sludge. Atblock 901, the moisture content of the dewatered sludge may be reduced.In some examples, this may be done using grinder or mill 2 as describedabove. For instance, sludge may be broken up in the presence of hot airto form a powder having a moisture content of less than about 10%. Thehot air may absorb at least a portion of the moisture contained in thesludge. In some examples, the dewatered sludge may be pre-heated beforeentering the grinder or mill 2 using, for example, sludge pre-heater 61.

At block 903, the dried powder may be separated from the at leastpartially saturated gas generated at block 901. In some examples, thismay be done using gas-solids separator 4 as described above. Forinstance, gas-solids separator 4 may be operable to separate the powderfrom the at least partially saturated gas generated by grinder or mill 2and deposit the separated powder into a dry fuel bin 5. In someexamples, gas-solids separator 4 may be a cellular type separator andmay include one or more Stairmand-type cyclones to clean gas vented tothe secondary side of gas-solids separator 4.

At block 905, the moisture content of the at least partially saturatedgas may be reduced by reducing the temperature of the at least partiallysaturated gas. In some examples, this may be done using condensing-typescrubber 7 as described above. For instance, the at least partiallysaturated gas may be passed through a series of tubes that are cooled byambient water received from a water source 8. As the at least partiallysaturated gas cools below the dew point of the gas moisture, at least aportion of the moister condenses out of the gas. In some examples usingpre-heated sludge, the ambient water exiting condensing-type scrubber 7may be used to pre-heat the dewatered sludge.

At block 907, the reduced-temperature gas generated at block 905 may bepre-heated. In some examples, the reduced-temperature gas generated atblock 905 may be pre-heated using a jacket formed around an air-heater.For example, the reduced-temperature gas may be heated using jacket 50of air-heater 12. Alternatively or in addition, in some examples, thereduced-temperature gas generated at block 905 may be pre-heated usingpre-heater 40 as described above. For instance, the gas cooled bycondensing-type scrubber 7 may be heated using a special ductarrangement operable to heat the reduced-temperature gas. In someexamples, the reduced-temperature gas may be pre-heated using gas thatwas previously heated by air-heater 12.

At block 909, the pre-heated gas may be heated. In some examples, thismay be done using air-heater 12 and dual fuel burner 13 as describedabove. For instance, dual fuel burner 13 may be operable to burn thepowder dried at grinder or mill 2, gas or oil from a supplementary fuelsource 18, or combinations thereof.

At block 911, at least a portion of the ash contained in the heated gasmay be removed. In some examples, this may be done using a grit arrestor19 as described above. In particular, grit arrestor 19 may have a designsimilar to that of gas-solids separator 4 and may be operable to removeat least a portion of the ash contained in the gas heated by air-heater12.

At block 913, at least a portion of the heated gas may be directed to amill. In some examples, this may be done by directing a portion of theoutput of grit arrestor 19 to mixing duct 3 and grinder or mill 2, asdescribed above. For example, in some examples, grit arrestor 19 may beoperable to direct a majority (e.g., 70%-75%) of the gas that entersgrit arrestor 19 to mixing duct 3 and grinder or mill 2. In otherexamples, a portion of the gas cleaned by grit arrestor 19 may bedirected to grinder or mill 2 while the remaining portion of the cleanedgas may be directed to hot wind box 63 to pre-heat the ambient air fromsecondary air supply inlets 16. Ash and the remaining gas may be ventedoff the secondary side of grit arrestor 19 to be surplussed from thesystem. Specifically, the ash the remaining gas from grit arrestor 19may be directed to water-mist-cooling system 20, ash cyclones 22,terminal condensing scrubber 24, and discharged from the system throughfinal discharge stack 29. In some examples, the warmed ambient waterfrom condensing scrubber 24 may be used to pre-heat the sludge fromstorage unit 1 at sludge pre-heater 61.

In other examples, a portion of the cleaned gas output of grit arrestor19 may be directed to hot wind box 63 by gas diverter valve 65 topre-heat the ambient air from secondary air supply inlets 16.

In other examples, at least a portion of the heated gas may be directedto grinder or mill 2 by tapping duct 43 as described above. Inparticular, tapping duct 43 may be operable to recirculate a majority(in some examples, at least 70%) of the gas heated by air-heater 12 bydirecting the heated gas to grinder or mill 2 to be used to dry sludge.In some examples, the remaining heated gas may be diverted to pre-heater40 to pre-heat the reduced-temperature gas generated by condensing-typescrubber 7. In other examples, the diverted gas may be used to pre-heatthe reduced-temperature gas generated by condensing-type scrubber 7 andthe mixture of ambient gas and fuel supplied to dual fuel burner 13.

It should be appreciated that while the blocks of process 900 areprovided in a particular order, the blocks can be performed in any orderand process 900 can include all or a portion of the blocks listed above.

Those skilled in the art will recognize that the operations of somevariations may be implemented using hardware, software, firmware, orcombinations thereof, as appropriate. For example, some processes can becarried out using processors or other digital circuitry under thecontrol of software, firmware, or hard-wired logic. (The term “logic”herein refers to fixed hardware, programmable logic and/or anappropriate combination thereof, as would be recognized by one skilledin the art, to carry out the recited functions.) Software and firmwarecan be stored on computer-readable storage media. Some other processescan be implemented using analog circuitry, as is well known to one ofordinary skill in the art. Additionally, memory or other storage, aswell as communication components, may be employed in embodiments of theapparatus and methods described herein.

FIG. 10 illustrates a typical computing system 1000 that may be employedto carry out processing functionality in some variations of the process.For instance, computer system 1000 may be used to control one or moreelements of the exemplary treatment systems described above. Thoseskilled in the relevant art will also recognize how to implement theapparatus and methods described herein using other computer systems orarchitectures. Computing system 1000 may represent, for example, adesktop, laptop, or notebook computer, hand-held computing device (PDA,cell phone, palmtop, etc.), mainframe, supercomputer, server, client, orany other type of special or general purpose computing device as may bedesirable or appropriate for a given application or environment.Computing system 1000 can include one or more processors, such as aprocessor 1004. Processor 1004 can be implemented using a general orspecial purpose processing engine such as, for example, amicroprocessor, controller, or other control logic. In this example,processor 1004 is connected to a bus 1002 or other communication medium.

Computing system 1000 can also include a main memory 1008, preferablyrandom access memory (RAM) or other dynamic memory, for storinginformation and instructions to be executed by processor 1004. Mainmemory 1008 also may be used for storing temporary variables or otherintermediate information during execution of instructions to be executedby processor 1004. Computing system 1000 may likewise include aread-only memory (“ROM”) or other static storage device coupled to bus1002 for storing static information and instructions for processor 1004.

The computing system 1000 may also include information storage mechanism1010, which may include, for example, a media drive 1012 and a removablestorage interface 1020. The media drive 1012 may include a drive orother mechanism to support fixed or removable storage media, such as ahard disk drive, a floppy disk drive, a magnetic tape drive, an opticaldisk drive, a CD or DVD drive (R or RW), or other removable or fixedmedia drive. Storage media 1018, may include, for example, a hard disk,floppy disk, magnetic tape, optical disk, CD or DVD, or other fixed orremovable medium that is read by and written to media drive 1012. Asthese examples illustrate, the storage media 1018 may include acomputer-readable storage medium having stored therein particularcomputer software or data.

In some variations, information storage mechanism 1010 may include othersimilar instrumentalities for allowing computer programs or otherinstructions or data to be loaded into computing system 1000. Suchinstrumentalities may include, for example, a removable storage unit1022 and an interface 1020, such as a program cartridge and cartridgeinterface, a removable memory (for example, a flash memory or otherremovable memory module) and memory slot, and other removable storageunits 1022 and interfaces 1020 that allow software and data to betransferred from the removable storage unit 1022 to computing system1000.

In some variations, computing system 1000 can also include acommunications interface 1024. Communications interface 1024 can be usedto allow software and data to be transferred between computing system1000 and external devices. Non-limiting examples of communicationsinterface 1024 can include a modem, a network interface (such as anEthernet or other NIC card), a communications port (such as for example,a USB port), a PCMCIA slot and card, a PCI interface, etc. Software anddata transferred via communications interface 1024 are in the form ofsignals which can be electronic, electromagnetic, optical, or othersignals capable of being received by communications interface 1024.These signals are provided to communications interface 1024 via achannel 1028. This channel 1028 may carry signals (e.g., signals to andfrom sensors or controllers) and may be implemented using a wirelessmedium, wire or cable, fiber optics, or other communications medium.Some examples of a channel include a phone line, a cellular phone link,an RF link, a network interface, a local or wide area network, and othercommunications channels.

The terms “computer program product” and “computer-readable storagemedium” may be used generally to refer to non-transitory storage media,such as, for example, memory 1008, storage device 1018, or storage unit1022. These and other forms of computer-readable storage media may beinvolved in providing one or more sequences of one or more instructionsto processor 1004 for execution. Such instructions, generally referredto as “computer program code” (which may be grouped in the form ofcomputer programs or other groupings), when executed, enable thecomputing system 1000 to perform features or functions of embodiments ofthe apparatus and methods, described herein.

In some variations where the elements are implemented using software,the software may be stored in a computer-readable storage medium andloaded into computing system 1000 using, for example, removable storagedrive 1012 or communications interface 1024. The control logic (in thisexample, software instructions or computer program code), when executedby the processor 1004, causes the processor 1004 to perform thefunctions of the apparatus and methods, described herein.

It will be appreciated that, for clarity purposes, the above descriptionhas described embodiments of the apparatus and methods described hereinwith reference to different functional units and processors. However, itwill be apparent that any suitable distribution of functionality betweendifferent functional units, processors, or domains may be used withoutdetracting from the apparatus and methods described herein. For example,functionality illustrated to be performed by separate processors orcontrollers may be performed by the same processor or controller. Hence,references to specific functional units are only to be seen asreferences to suitable means for providing the described functionality,rather than as indicative of a strict logical or physical structure ororganization.

While specific components and configurations are provided above, it willbe appreciated by one of ordinary skill in the art that other componentsvariations may be used. Additionally, although a feature may appear tobe described in connection with a particular embodiment, one skilled inthe art would recognize that various features of the describedembodiments may be combined. Moreover, aspects described in connectionwith an embodiment may stand alone.

Furthermore, although individually listed, a plurality of means,elements, or method steps may be implemented by, for example, a singleunit or processor. Additionally, although individual features may beincluded in different claims, these may possibly be advantageouslycombined, and the inclusion in different claims does not imply that acombination of features is not feasible and/or advantageous. Also, theinclusion of a feature in one category of claims does not imply alimitation to this category, but rather the feature may be equallyapplicable to other claim categories, as appropriate.

What is claimed is:
 1. A system for processing dewatered sludge, thesystem comprising: at least one of a mill or grinder operable to:receive high-temperature gas; receive sludge; and reduce a moisturecontent of the sludge by breaking the sludge into a dried powder in thepresence of the high-temperature gas, wherein the high-temperature gasabsorbs at least a portion of the moisture content of the sludge to format least partially saturated gas; a first separator operable to separatethe dried powder from the at least partially saturated gas; a firstcondenser operable to reduce a moisture content of the at leastpartially saturated gas by reducing a temperature of the at leastpartially saturated gas to form a reduced-temperature gas; a heateroperable to heat the reduced-temperature gas to form a heated gas; asecond separator operable to separate at least a portion of ashcontained in the heated gas from the heated gas, wherein the secondseparator is further operable to direct a first portion of the heatedgas to the at least one of the mill or grinder to be used as thehigh-temperature gas; and an output system operable to discharge the ashand a second portion of the heated gas from the system.
 2. The system ofclaim 1, wherein the sludge comprises at least one of digested sludge,undigested sludge, fresh animal waste, aged animal waste, oragricultural food waste.
 3. The system of claim 1, wherein the heatercomprises an air-heater jacket operable to receive thereduced-temperature gas from the first condenser, and wherein theair-heater jacket is further operable to cause the reduced-temperaturegas to travel over at least a portion of a surface of the heater.
 4. Thesystem of claim 1, wherein the heater comprises a burner operable toburn a mixture of ambient air and at least a portion of the driedpowder.
 5. The system of claim 4, wherein the burner is further operableto burn a gas or oil.
 6. The system of claim 4, further comprising a hotwind box, wherein a portion of an output of the second separator is usedto pre-heat the ambient air in the hot wind box.
 7. The system of claim1, wherein the first condenser is operable to receive water at a firsttemperature, the water to be used to reduce the temperature of the atleast partially saturated gas, and wherein the first condenser isfurther operable to output the water at a second temperature that ishigher than the first temperature.
 8. The system of claim 1, wherein thefirst portion of the heated gas comprises a majority of the heated gas.9. The system of claim 1, wherein the output system comprises: awater-mist-cooling system operable to reduce a temperature of the secondportion of the heated gas to form cooled gas; a third separator operableto separate at least a portion of ash contained in the cooled gas fromthe cooled gas, wherein the third separator is further operable todischarge the ash separated from the cooled gas from the system; asecond condenser operable to reduce a moisture content of the cooled gasby reducing a temperature of the cooled gas to form a reduced moisturegas; and a fan operable to discharge the reduced moisture gas from thesystem.
 10. The system of claim 9 further comprising a sludgepre-heater, wherein an output of the second condenser is used topre-heat the sludge in the sludge pre-heater.
 11. A system forprocessing dewatered sludge, the system comprising: at least one of amill or grinder operable to: receive high-temperature gas; receivesludge; and reduce a moisture content of the sludge by breaking thesludge into a dried powder in the presence of the high-temperature gas,wherein the high-temperature gas absorbs at least a portion of themoisture content of the sludge to form at least partially saturated gas;a first separator operable to separate the dried powder from the atleast partially saturated gas; a condenser operable to reduce a moisturecontent of the at least partially saturated gas by reducing atemperature of the at least partially saturated gas to form areduced-temperature gas; a pre-heater operable to pre-heat thereduced-temperature gas to form pre-heated gas; a heater operable toheat the pre-heated gas to form heated gas; a second separator operableto separate at least a portion of ash contained in the heated gas fromthe heated gas; and a first tapping duct operable to recirculate atleast a portion of the heated gas by directing the at least a portion ofthe heated gas to the at least one of the mill or grinder, wherein theat least a portion of the heated gas is to be used in the at least oneof the mill or grinder as the high-temperature gas.
 12. The system ofclaim 11, wherein the sludge comprises at least one of digested sludge,undigested sludge, fresh animal waste, aged animal waste, oragricultural food waste.
 13. The system of claim 11, wherein the heatercomprises an air-heater jacket operable to receive the pre-heated gasfrom the pre-heater, and wherein the air-heater jacket is furtheroperable to cause the pre-heated gas to travel over at least a portionof a surface of the heater.
 14. The system of claim 11, wherein thefirst tapping duct is operable to recirculate a majority of the heatedgas received at the tapping duct.
 15. The system of claim 11, whereinthe pre-heater is operable to pre-heat the reduced-temperature gas usingat least a portion of the heated gas that is not directed to the atleast one of the mill or grinder by the tapping duct.
 16. The system ofclaim 15, wherein the at least a portion of the heated gas that is notdirected to the at least one of the mill or grinder is removed from thesystem.
 17. The system of claim 11, wherein the heater comprises aburner operable to burn a mixture of ambient air and at least a portionof the dried powder.
 18. The system of claim 17, wherein the burner isfurther operable to burn a gas or oil.
 19. The system of claim 17,further comprising a mixing valve operable to combine the mixture ofambient air and the at least a portion of the dried powder with aportion of the heated gas not directed to the at least one of the millor grinder by the first tapping duct.
 20. The system of claim 19,further comprising a second tapping duct operable to direct, to themixing valve, the portion of the heated gas not directed to the at leastone of the mill or grinder.
 21. A method for processing dewateredsludge, the method comprising: reducing, in at least one of a mill orgrinder, a moisture content of a dewatered sludge by breaking thedewatered sludge into a dried powder in the presence of high-temperaturegas, wherein the high-temperature gas absorbs at least a portion of themoisture content of the dewatered sludge to form at least partiallysaturated gas; separating the dried powder from the at least partiallysaturated gas; reducing a moisture content of the at least partiallysaturated gas by reducing a temperature of the at least partiallysaturated gas to form a reduced-temperature gas; pre-heating thereduced-temperature gas to form pre-heated gas; heating the pre-heatedheated gas to form heated gas; separating at least a portion of ashcontained in the heated gas from the heated gas; and recirculating atleast a portion of the heated gas by directing the at least a portion ofthe heated gas to the at least one of the mill or grinder, wherein theat least a portion of the heated gas is to be used in the at least oneof the mill or grinder as the high-temperature gas.
 22. The method ofclaim 21, wherein a majority of the heated gas is recirculated to the atleast one of the mill or grinder.
 23. The method of claim 21, whereinseparating the dried powder from the at least partially saturated gas isperformed using a first cyclone separator, and wherein separating atleast a portion of the ash contained in the heated gas from the heatedgas is performed using a second cyclone separator.
 24. The method ofclaim 21, wherein heating the pre-heated heated gas is performed using aburner operable to burn a mixture of ambient air and at least a portionof the dried powder.
 25. The method of claim 24, further comprisingcombining the mixture of ambient air and the at least a portion of thedried powder with a portion of the heated gas not directed to the atleast one of the mill or grinder.
 26. The method of claim 24, wherein aweight of the ambient air is equal to a weight of the portion of theheated gas that is not directed to the at least one of the mill orgrinder.
 27. The method of claim 21, wherein heating the pre-heated gasis performed using a heater comprising an air-heater jacket, and whereinthe air-heater jacket is operable to cause the pre-heated gas to travelover at least a portion of a surface of the heater.
 28. The method ofclaim 21 further comprising pre-heating the dewatered sludge beforereducing, in the at least one of the mill or grinder, the moisturecontent of a sludge by breaking the sludge into the dried powder in thepresence of high-temperature gas.